By Robert A. Hollander, P.E.
Water systems expend a huge amount of effort and resources to treating and distributing safe drinking water to their customers. So, they are particularly sensitive to situations of water flowing from a customer back into the distribution system with the possible introduction of foreign substances or unapproved water sources.
This article will address backflow prevention and cross connection control.
What is “backflow”?
“Backflow” means the reverse flow of water, fluid, or gas caused by back pressure or back siphonage (ref. Code of Colorado Regulations. Water Quality Control Commission 11.39(1)). With public water systems, this can happen if water flows from the customer back into the distribution system due to
- either higher pressure on the customer side compared to the system side, or
- due to a loss of pressure on the system side, resulting in a vacuum and drawing water from the customer side into the distribution system.
What is a “cross connection”?
A “cross connection” means any physical connection or arrangement between two otherwise separate piping systems – one of which contains potable water and the other either water of unknown or questionable safety or steam, gas or chemical, whereby there exists the possibility for flow from one system to the other, with the direction of flow depending on the pressure differential between the two systems (ref. UPC 2006).
Examples of backflow and cross connections are demonstrated below.
There are no federal backflow prevention or cross connection control laws or regulations. Therefore, it is up to the states to establish the authority, usually through statutes, to create the programs and subsequent regulations. State regulations provide a general outline of what these programs should include and require public water systems to comply by developing and implementing the programs.
Public water systems must establish local regulations or ordinances that provide the requirements and details of the backflow prevention and cross connection control program. The ordinances should describe:
- when a backflow prevention assembly is required,
- the type of device needed,
- specifications for the devices, and
- a requirement for periodic testing of the devices.
They can also require that individuals that perform the testing be specially certified to do so. Generally, most commercial (e.g. restaurants, auto repair shops, schools with laboratories) and industrial facilities will require some level of protection. Most state regulations exempt single family residential properties unless a cross connection problem is identified.
Many states and local jurisdictions rely on the International or Uniform Plumbing Code to provide guidance on baseline backflow protection measures.
There are several types of backflow prevention devices. The type required for the installation depends on the risk of backflow and characteristics of materials that may enter the water system. The greater the risk and danger presented by the material (e.g. toxic chemicals) the higher the level of protection needed.
Below are backflow prevention devices in descending order of protection.
- Air gap (generalized diagram)
- Reduced Pressure Principal Backflow Preventer (two individually operated check valves separated by a relief valve)
- Double check valve assembly (two individually operated check valves in series)
- Atmospheric vacuum breaker (found on water risers serving residential homes)
Additional backflow program requirements
State rules or local ordinances may include requirements for backflow prevention assemblies, such as specifications and certifications of backflow prevention assemblies. Generally, the backflow prevention devices should be approved by a third-party certifying agency. The devices should also be equipped with cocks on both ends in order to periodically test for adequate function.
Backflow prevention devices should be located as close to the service connection as is practicable. This is to allow testing of the devices while minimizing intrusion onto the property of the consumer. Testing of backflow prevention assemblies should be performed after installation, relocation, or repair, and on an annual basis thereafter to ensure adequate operation.
The management of a backflow prevention program should include some key elements. The utility should develop and maintain a list of establishments that require backflow prevention (e.g. commercial, industrial entities) and the type of device employed. It is recommended that property addresses of these establishments be linked to actual devices serving the property (e.g. using device model numbers and/or serial numbers). Therefore, the preparation and maintenance of records of regulated backflow prevention assemblies, including annual testing schedules and results are essential.
To provide the greatest assurance that devices are operating properly, backflow prevention assembly testers should be certified to perform their responsibilities. This involves specialized training above and beyond general plumbing skills. Water systems should maintain lists of certified testers who operate within their jurisdictions and make that list readily available to customers who would need those services. Some states may also require the administrator of the backflow prevention and cross connection control program for the water system also be specifically certified to carry out this responsibility. This provides some credibility for the local program to certified testers.
Compliance assistance followed by enforcement may be necessary to ensure all customers and or their testers comply. Enforcement should follow procedures established in an Enforcement Response Plan or Enforcement Escalation Policy and should be coordinated with the water system or local entity legal department, to the degree necessary. Maintenance of accurate, up to date, backflow device and testing records is critical for successful enforcement when it becomes necessary.
Finally, some states will require water systems to periodically report, usually annually, to the primacy agency (i.e. state agency responsible for enforcement of drinking water regulations) on the status of the backflow prevention program. The data requirements for managing these programs, especially for middle and large water systems can be daunting. Technology can assist with managing the data, backflow prevention devices, testing schedules and tester certification status and the program in general.